Water induction in steam turbines, which generally may be defined as water or cold steam in the steam lines, is a problem that affects the life and performance of the turbine. This anomaly is currently detected by low temperature measurements or abrupt changes in temperatures in the steam lines. These temperature readings generally are taken with thermocouples, which generally are installed in pairs in the upper and lower halves of the casing of a steam line at several points axially in outer shell. Under normal conditions, the lower and upper thermocouple will indicate approximately the same temperature. However, an abrupt decrease in temperature of the lower thermocouple while the upper thermocouple remains essentially unchanged or a significant drop in temperature measured in both thermocouples below a predetermined level may indicate the presence of water in the steam line.
In general, known systems rely on abrupt temperature differentials in the thermocouple pair to detect water induction. These systems indicate that water induction is occurring when the temperature differential between the upper and lower thermocouple exceeds a predetermined limit. However, fluctuations that occur during the normal operation of a steam turbine can cause such systems to show water induction occurring when it is not. As such, these known systems give a number of “false alarms.” Over time, regularly occurring false alarms can cause real water induction events to be ignored, which can have a serious impact on the health of the turbine system. At a minimum, false alarms that force the system operator to confirm that water induction is not occurring waste time and resources. Thus, there is a need for improved methods and systems for reliably determining when water induction is occurring in steam turbines. Other objects, features and advantages of the invention will be found throughout the following description, drawings and claims.